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ENVIRONMENTAL IMPACT ASSESSMENT OF
AVIATION EMISSIONS REDUCTION
THROUGH THE IMPLEMENTATION OF
COMPOSITE MATERIALS
Andrew J. Timmis1, Alma Hodzic*2, Lenny Koh1, Michael Bonner2, Constantinos Soutis3,
Andreas W. Schäfer4, Lynnette Dray5
* Corresponding author
1 Centre for Energy, Environment and Sustainability, Management School, The University of
Sheffield, UK
2 Composite Systems Innovation Centre, Department of Mechanical Engineering, The University
of Sheffield, UK
3 Aerospace Research Institute, Faculty of Engineering & Physical Sciences, University of
Manchester, UK
4 UCL Energy Institute, University College London, UK
5 Institute for Aviation and the Environment, The University of Cambridge, UK
Corresponding Author Details:
Professor Alma Hodzic
e-mail: a.hodzic@sheffield.ac.uk
Tel: +44 (0)114 2227720
2
ABSTRACT 1
Purpose 2
Carbon fiber reinforced polymers (CFRP) have been developed by the aviation industry to 3
reduce aircraft fuel burn and emissions of greenhouse gases. This study presents a lifecycle 4
assessment (LCA) of an all-composite airplane, based on a Boeing 787 Dreamliner. The global 5
transition of aircraft to those of composite architecture is estimated to contribute 20-25% of 6
industry CO2 reduction targets. A secondary stage of the cradle-to-grave analysis expands the 7
study from an individual aircraft to the global fleet. 8
Materials and Methods 9
An LCA was undertaken utilising Sima Pro 7.2 in combination with Ecoinvent. Eco-indicator 10
99 (E) V2.05 Europe EI 99 E/E was the chosen method to calculate the environmental impact of 11
the inventory data. The previously developed Aviation Integrated Model was utilised to construct 12
a scenario analysis of the introduction of composite aircraft against a baseline projection, through 13
to 2050, to model CO2 emissions due to their particular relevance in the aviation sector. 14
Results and Discussions 15
The analysis demonstrated CFRP structure results in a reduced single score environmental 16
impact, despite the higher environmental impact in the manufacturing phase, due to the increased 17
fossil fuel use. Of particular importance is that CFRP scenario quickly achieved a reduction in 18
CO2 and NOx atmospheric emissions over its lifetime, due to the reduced fuel consumption. The 19
modeled fleet-wide CO2 reduction of 14-15% is less than the quoted emission savings of an 20
individual aircraft (20%) because of the limited fleet penetration by 2050, and the increased 21
demand for air travel due to lower operating costs. 22
Conclusions 23
3
The introduction of aircraft based on composite material architecture has significant 24
environmental benefits over their lifetime compared to conventional aluminum based 25
architecture, particularly with regards to CO2 and NOx a result of reduced fuel burn. The 26
constructed scenario analyses the interactions of technology and the markets they are applied in, 27
expanding on the LCA. In this case, an observed fleet wide reduction of CO2 emission of 14-28
15% compared to an individual aircraft of 20%. 29
KEYWORDS: aviation emissions, carbon fiber reinforced polymers, composite aircraft, global 30
warming, life cycle assessment 31
1. INTRODUCTION 32
The combustion products of aviation fuel includes several gaseous emissions, mainly CO2, 33
nitrogen oxides (NOx), water vapor (H2O), sulphur oxides (SOx) and soot; CO2, NOx and H2O 34
being greenhouse gases. The Intergovernmental Panel on Climate Change (IPCC, 1999) have 35
highlighted the potential impact of increased levels of greenhouse gases, both CO2 and non-CO2, 36
on the global atmospheric environment. The aviation sector currently produces around 0.71 37
GtCO2 (2%) of global energy related CO2 emissions (IPCC, 2014). Though this is small in 38
comparison to the transport sector (Duflou et al, 2009) as a whole 6.7 GtCO2 (23%), aviation 39
emissions are forecast to increase through to 2050 by around 3-4% per annum due to the 40
increasing demand, approximately 5% per annum through to 2030 (Airbus, 2011; Boeing, 41
2013a), surpassing forecast improvements in fuel efficiency of 1-1.5% per annum (Kahn Ribeiro, 42
2007). It is appreciated by the aviation industry itself that it is unacceptable to have an 43
increasing share of global greenhouse gas emissions (IATA, 2009). 44
The aviation industry has a range of targets regarding the future control of carbon dioxide 45
emissions, the main anthropogenic greenhouse gas under consideration, through to 2050. Targets 46
4
include 1.5% per annum improvement in fleet fuel efficiency, carbon neutral growth from 2020 47
and a reduction in net CO2 emissions of 50% by 2050 (ACARE, 2011; ICAO, 2013). Currently, 48
the emission of greenhouse gases from the international aviation industry is unregulated and is 49
not included in the scope of the Kyoto Protocol. Aviation is included in the European Union 50
Emission Trading Scheme (EU ETS). International aviation emissions emitted in European 51
airspace were temporarily covered by the EU Emissions Trading Scheme in 2012; at the time of 52
writing, legislation has subsequently been withdrawn to allow the development of an 53
international agreement and strategy to reduce international aviation emissions by the 54
Iinternational Civil Aviation Organization (ICAO). 55
It is widely recognised that gaseous emissions at high altitudes are more environmentally 56
damaging than those at ground level, due to increased interaction with gases in the atmosphere. 57
A parameter used to quantify the effect of aviation emission is the Radiative Forcing (RF) Index, 58
which is a measure of the impact of an agent on the energy balance of the earth’s atmosphere. 59
Aircraft operation involves the emission of (a) directly radiatively active substances (e.g. CO2 or 60
water vapor); (b) chemical species that produce or destroy radiatively active substances (e.g. 61
NOx, which modifies ozone concentration); and (c) substances that trigger the generation of 62
aerosol particles or lead to changes in natural clouds (e.g. contrails). These emissions and cloud 63
effects modify the chemical and particle microphysical properties of the upper atmosphere, 64
resulting in changes in RF of the earth’s climate system, which can potentially lead to climate 65
change impacts and ultimately result in damage and welfare/ecosystem loss (Beck et al, 2009). 66
Emissions of particulate materials can affect both the environment, contributing to climate 67
change, and can be hazardous to human health, particularly if they are produced in the lower part 68
of the atmosphere, around airports for example. Thus, it is important to analyse the life cycle of 69
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aircraft systems and structures in as much detail as possible, in order to understand the long-term 70
impact on the human environment and the earth’s ecosystem. However, on a global scale, CO2 71
and NOx emissions are greatest contributors to the global environmental impact, with the former 72
contributing thousands of times more emissions than other products of fuel burning in aviation. 73
In addition to growing concern about the environmental impact of aviation, aviation fuel is the 74
single most significant component of an airline operating cost, some 30-40% (IATA, 2009); this 75
cost is highly dependent on a volatile oil price (EC, 2008). With profit margins for the financial 76
year 2013/14 expected to be as little as 1.8% (IATA, 2012) cost control within the airline 77
industry is highly important. 78
Carbon fiber reinforced polymer (CFRP), an advanced composite material, has been utilised as 79
a structural component in the airframes of the ‘next generation’ of aircraft due to its reduced 80
weight in comparison to aluminum. The Boeing 787 Dreamliner is a case in point, with 50% by 81
weight consisting of composite materials. Airframe manufacturers claim that this next 82
generation in airframe architecture can reduce fuel use, and subsequently CO2, by around 20-83
25% (Airbus, 2012; Boeing, 2013b). 84
This study will provide an overview of the full LCA impact analysis and focus on the emission 85
of CO2 from the combustion of jet fuel. Whilst it is widely recognised that the combustion of jet 86
fuel results in the emission of a range of pollutants, each with potentially detrimental 87
atmospheric environmental impacts, CO2 has been selected due to the importance placed on its 88
emissions by the current policy, due to its long lifetime in the atmosphere. 89
The primary purpose of this study is to present a life cycle assessment of a section of a 90
composite material aircraft, to understand the environmental impact on an individual aircraft 91
scale. This data is further used to study the impact of the introduction of an aircraft with a 92
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composite material architecture on the projected global fleet emissions through to 2050. This 93
combined simulation aims to model the effect of a transition in the global aviation fleet to the 94
next generation of aircraft architecture. CO2 and other environmental impacts are calculated 95
using socio-economic scenarios from a set of integrated energy-economy-environment models 96
against a baseline, and the results are subsequently discussed in relation to the industry targets 97
and projections of potential savings. 98
The study is here presented in two distinct parts. Methods – Stage 1 present a full life cycle 99
assessment of manufacturing, in-use and disposal stages of the composite and aluminium 100
aircrafts, including the results from this part of the study (Results – Stage 1). Methods – Stage 2 101
presents the method and outputs of the Aviation Integrated Model scenarios, including the results 102
(Results – Stage 2). Both stages of the analysis are integrated through the Discussion covering 103
numerous aspects of this complex multidisciplinary analysis and the major findings are 104
summarised in the Conclusions. 105
2. METHODS - STAGE 1 106
This paper is presented as a two-phase study; the method of enquiry of phase one is presented 107
below and subsequently the results are presented. The secondary stage of analysis is presented 108
after the LCA results. 109
2.1 LCA methodology and software 110
A Life Cycle Assessment is a method of quantifying the environmental impact of a product or 111
service throughout its lifecycle from raw material extraction and processing, use phase and end 112
of life disposal (ISO, 2006). The importance of LCAs is their ability to inform where 113
environmental impacts occur and their relative importance. This enables interventions into the 114
product life-cycle that are appropriate and prevent problem-shifting of either environmental 115
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products from one to another or shifting environmental impacts from one phase of a products 116
lifecycle to another (Rebitzer, 2004). 117
A comparative LCA has been conducted on Section 46 of the Boeing 787 fuselage, due to the 118
public availability of the manufacturing data required for LCA study. The Boeing 787 airframe 119
was chosen due to the high proportion of CFRP utilised within its structure (approximately 50%) 120
(Boeing, 2013b). 121
The LCA of fuselage section 46 of Boeing 787 was performed utilising Sima Pro 7.2 in 122
combination with the Ecoinvent database. Ecoinvent contains industrial lifecycle inventory data 123
on energy supply, resource extraction, material supply, chemicals, metals, agriculture, waste 124
management services and transport services. Eco-indicator 99 (E) V2.05 Europe EI 99 E/E was 125
the chosen method to calculate the environmental impact of the inventory data. This method 126
enables the aggregation of different impact categories into a single score value, and thus allows a 127
relative comparison between different environmental impacts to be conducted. 128
Technical data from the published literature has been utilised for the LCA where available 129
(Boeing, 2013b; Beck et al, 2009). Due to commercial sensitivity associated with the technical 130
design of the section and manufacturing processes, the research team, where appropriate, used 131
informed judgment to estimate unavailable processes data. This pragmatic simplification of the 132
LCA has been considered appropriate by the wider LCA literature (De Beaufort-Langeveld, 133
1997). Where appropriate, such assumptions are identified in this paper. 134
2.2 LCA scenarios 135
The LCA undertaken in this study is presented in two stages: the first stage compares the 136
equivalent sections manufactured from CFRP and Aluminum alloy through manufacturing and 137
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disposal phases, and the second phase takes into consideration of the operational emissions, and 138
hence the full life cycle,. 139
2.2.1 LCA data collection and system boundaries 140
A typical weight saving of 20% (widely reported by the industry) was used as the basis for 141
comparison between the CFRP and Aluminum alloy structure (Campbell, 2004). Boeing 787 142
airframe consists of several one-piece CFRP tubesections. Section 46, being one of these tube 143
sections, was manufactured by Alenia Aeronautica, Italy. The reported mass of Section 46 is 144
4000lb (1814 kg) (Norris, 2009). The total reported mass is assumed to include the fuselage skin, 145
frames, stringers and floor beams. Due to the lack of specific data regarding the structure's 146
geometric properties, the section is simplified to a uniform tube shape. The effective thickness of 147
the uniform tube, calculated from the volume of the section and density of the material, is greater 148
than the fuselage skin thickness of Section 46, to account for the additional parts. The simplified 149
tube section was reported to be manufactured using a uniform automated tape laying 150
manufacturing process. 151
The length and external diameter of the section are 33ft (10.06m) and 19ft (5.79m) 152
respectively. The CFRP utilised in this study is assumed to have a density typical of the 153
material, 0.0556lb/in3 (0.0277 kg/cm3). Applying the relationship between mass, as previously 154
reported, and density, the effective thickness of the simplified tube fuselage wall was 155
approximated at 12.95mm. This is a justifiable assumption, considering that the mass of the 156
section will have the influence on LCA, rather than its dimensions. 157
Prior to the manufacturing consideration, the cradle LCA scope is defined by production of 158
raw materials for each type of aircraft. CFRP consists of carbon fibres and epoxy resin. Carbon 159
fibres are produced from polyacrylonitrile (PAN) based fibers through a process called the 'PAN 160
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process', during which the fibres are carbonised at temperatures between 1800 and 2700 °F (980 161
and 1480 °C). The aerospace grade CFRP utilised in manufacturing is assumed to be composed 162
of 65% carbon fibre and 35% epoxy resin by weight, standard fractions in aerospace grade 163
CFRPs. The pre-preg tape is placed onto a cylindrical mandrel using automated tape placement 164
process and then cured in an autoclave. The layering process is repeated till the calculated 165
fuselage wall thickness is achieved. The electricity consumption, and subsequent raw material 166
consumption and emissions of electricity production, for the autoclave and pre-preg tape 167
placement, via an Automated Fibre Placement machine, has been considered. A typical Italian 168
electricity production mix has been considered. 169
The AFP robot used to manufacture Section 46 is manufactured by Ingersoll, with the energy 170
consumption estimated to be at its maximum capacity of 16,000 kWh. 171
As a comparison, the section 47 and 48 of similar dimensions are manufactured by Vought, 172
and cured in an autoclave with a power rating of 12,000 kW for a period of 8hrs, hence an 173
estimated total energy consumption was 96,000 kWh. 174
The disposal of the composite section is assumed to be landfill. This assumption is discussed 175
in greater details in the LCA results section. The parameters used in LCA of manufacturing of 176
the composite section were intentionally chosen at the extreme end, in order to avoid any 177
potential bias towards the utilisation of composite materials compared to their metallic 178
counterparts. It was expected that the operational stage LCA would be overwhelmingly 179
favourable towards utilisation of composites, due to the significant fuel savings and 180
proportionally lower life cycle emissions. 181
2.2.2 LCA of aluminum alloy structure manufacturing 182
10
Two scenarios have been presented for the conventional aerospace aluminum alloy analysis 183
and comparison. The buy-to-fly (BTF) ratio is the amount of metal utilised to manufacture a part, 184
and this can be as high as 25:1 for aerospace components. For an average commercial aircraft 185
the buy-to-fly ratio is estimated to be 8:1. Hence, two scenarios are presented below: Al 186
Scenario 1, an idealised scenario with a buy-to-fly ratio of 1:1 and Al Scenario 2 with a more 187
realistic and still Al favourable buy-to-fly ratio of 8:1. The two scenarios will be referred to as Al 188
Scenario 1 and Al Scenario 2 respectively, and will be used here as the variables representative 189
of the idealised and the standard manufacturing practice. 190
The mass of Al alloy utilised in the fuselage is estimated to be 25% more (Campbell, 2006) 191
than the CFRP section, 2267kg. The aluminum ingots are hot rolled and subsequently machined 192
into the final part. Recycling of aluminum is highly efficient requiring between 6-7% of the 193
energy required for primary production (IEA, 2009). In current practice, recycled aluminum is 194
not utilised in the production of aircraft parts. In SimaPro LCA software database, recycled 195
aluminum is credited with positive emissions. The disposal scenarios for this analysis are 196
assumed to be 100% recycling for aluminium in order to approach the generic lightweight 197
advantage of CFRP with the most onerous comparison for CFRP case. 198
2.2.3 Additional consideration of in-use phase 199
As previously stated, LCA covers all phases of a product lifecycle from manufacture, use and 200
final disposal. The following in-use analysis of Boeing 787 makes a number of initial 201
assumptions; one, the aircraft has a range of 14,000km (Boeing, 2013b) and a life-span similar to 202
a typical commercial aircraft of 30-years (Peel, 1995); two, the aircraft is assumed to operate 203
daily, leading to the distance travelled by an aircraft during its lifetime of 150 million km. 204
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For this stage of the analysis it is important to define the functional unit. The unit for 205
comparison is tonne-km (tkm); the mass of the comparable unit multiplied by the distance 206
travelled. 207
3. RESULTS – STAGE 1 208
3.1 LCA results – manufacture and disposal 209
Figure 1 shows the single score environmental impact for the three manufacturing and disposal 210
scenarios considered in this study. The CFRP manufacturing scenario is demonstrated to have 211
higher emissions than both Al Scenario 1 and Al Scenario 2, as expected, due to the higher 212
energy power consumed during the carbon fiber production. The most significant contributor to 213
the increased environmental burden is due to fossil fuel use, a parameter more evident in the 214
normalisation plot of the environmental impact categories in Figure 2. The standard Eco-215
indicator values are dimensionless, similar to units of currency. In the Eco-99 system, the unit of 216
measurement is called the Eco-indicator Point, Pt. The size of the Pt unit was chosen by Eco-99 217
to represent one thousandth of the annual environmental load of an average citizen in Europe. 218
The primary environmental impacts of concern within the aviation industry are the gaseous 219
emissions of CO2 and NOx (ACARE, 2002; IATA, 2009), however other contributing factors are 220
also analysed for a more complete understanding of the full environmental impact. Figure 3 221
quantifies the emissions of both gases through the manufacturing and disposal phase for the three 222
material scenarios. The same trend as seen in the single score environmental impact is present 223
here, with CFRP manufacturing being more environmentally burdensome, with respect to both 224
CO2 and NOx. 225
3.2 LCA results – consideration of in-use phase 226
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Figure 4 shows the single score environmental impact for the three full LCA scenarios 227
considered in this study. The assessment demonstrates that the CFRP section results in a 228
decreasing environmental impact when compared to both scenarios in Al alloy section analysis. 229
Additionally, the environmental burden in the three scenarios is dominated by the consumption 230
of jet-fuel in the in use phase, and in turn the environmental impact resulting from manufacturing 231
and disposal can be considered negligible or insignificant in all the scenarios, as shown in our 232
earlier study (Scelsi et al, 2011). 233
As previously, the emissions of NOx and CO2 are presented separately (Figure 5). The CFRP 234
section results in a significant decrease in the emissions of both gaseous substances, 19% and 235
20% respectively. 236
3.2.1 LCA break-even distance/time 237
An additional stage of analysis undertaken by this study determined the distance and the hours 238
of operation of an aircraft at which the CFRP section becomes environmentally beneficial. As 239
demonstrated in the previous section, it is in the ‘in-use’ phase that the CFRP reverses the 240
environmental deficit of production and disposal stage; the amount of hours of operation can be 241
estimated. By negating the ascent and descent stages of the aircraft flight-path and assuming that 242
the aircraft operates at a cruise speed of 950km/h (Boeing, 2013b) the operation time can be 243
determined. The cumulative single score impact of three modeled scenarios calculated the break 244
even distances for CFRP against Al1 and Al2 as 190,000km (210 hrs in operation) and 75,000km 245
(83 hrs) respectively. Likewise, break-even distances for both CO2 and NOx were calculated 246
(Table 1). 247
The results imply that the break-even point in the emissions consumption and savings is 248
achieved after only a few international flights, and the manufacturing emissions can be hence 249
13
neglected in the analysis of the global impact of aviation in the atmospheric emissions. The fuel 250
consumption savings play a far more important part in achieving the emissions savings in the 251
future air transport. 252
4. METHODS – STAGE 2 253
4.1 The AIM aviation systems model 254
As previously highlighted, the introduction of composite material aircraft has been identified 255
as a method of achieving long-range industry targets for carbon emission reduction (IATA, 256
2009). The motivation in the aviation industry to introduce composite material aircraft is for both 257
environmental and economic factors (Mason, 2007). The second stage of this study considers the 258
impacts of a transition of the global aviation fleet to composite aircraft models with the aim of 259
understanding how the aircraft variants are adopted in the global market and how the resulting 260
carbon emissions reductions compare to those estimated per-aircraft as above (Helms & 261
Lambrecht , 2007; Givoni & Rietveld , 2009). 262
This study utilises a previously developed model, the Aviation Integrated Modelling (AIM) 263
(Reynolds, 2007), to simulate global aviation system responses to changes in costs and available 264
technologies. AIM consists of seven interconnected modules modeling demand for air travel, 265
routing and scheduling, airline costs and technology adoption, flight routing and emissions, local 266
and global emissions impacts and regional economics, run iteratively until equilibrium between 267
demand and supply is reached. For this study we concentrate on CO2 and neglect the local 268
emissions and regional economics modules. 269
AIM requires internally consistent scenarios of future population, gross domestic product 270
(GDP) and oil prices to project demand and technology adoption. For these scenarios we use the 271
outputs of three integrated assessment models used for a U.S. climate change mitigation study 272
14
(Clarke et al, 2007): IGSM (Integrated Global System Model), MERGE (Model for Evaluating 273
the Regional and Global Effects) and MiniCAM (Mini-Climate Assessment Model), shown in 274
Table 2. Two technology scenarios were constructed: a baseline analysis, in which current 275
airframe technology continues to be used, and a second scenario where aircraft models utilising 276
composite materials technology are introduced. 277
The commercial aviation fleet is assumed to consist of three representative aircraft variants. 278
The defined aircraft variants have been determined by size with aircraft representing small 279
(narrow-body, short to medium range), medium (wide-body, medium to long range) and large 280
(wide-body, medium to long range) aircraft. The three aircraft variants are deemed to be 281
representative of the overwhelming majority of commercial aircraft classes as represented in 282
industry literature (Airbus, 2011; Boeing, 2013a). Table 3 summarises the physical 283
characteristics and relative performance of the reference conventional and composite aircraft 284
variants. 285
The composite material aircraft proposed for all size classes are assumed to be a suitable 286
substitute for 100% of the aircraft fleet of that category. The size class defined as large includes 287
those aircraft deemed very large, e.g. Airbus A380. The proportion of aircraft in the very large 288
class is only 5% of new passenger aircraft delivered in the period 2011-2030 (Airbus, 2011) and 289
is therefore not defined separately. 290
To better isolate the impact of composite materials, the modeling only considers the effect of a 291
transition in airframe technology and associated evolutionary improvements in engine 292
technology, from those used in the reference aircraft to composite material variants. The model 293
does not take into account any technology transition in aircraft engine technology (e.g. open-294
rotor engines), the use of biofuels, operational changes relating to air transport movements 295
15
(ATMs) or the introduction of emission trading. In addition, we do not consider the next 296
generation of aircraft after those modeled. For these reasons, total emissions are likely to err on 297
the high side of those achievable. 298
5. RESULTS – STAGE 2 299
5.1 AIM results 300
As discussed above, two technology scenarios are modeled for each of the three socio-301
economic scenarios: 302
I. Reference simulation – continuation of conventional technology, and 303
II. Availability of composite material aircraft. 304
The primary driver for the adoption of composite material aircraft is the oil price, which 305
influences whether fuel-saving technologies will be cost-effective (Table 2). 306
16
307 Figure 6 (a, b and c [top row]) shows the total number of aircraft in the global fleet and the 308
proportion of composite aircraft. The total size of the fleet by 2050 is predicted to be between 309
95, 000 and 77, 500 aircrafts. In all three socio-economic scenarios by 2050 composite material 310
aircraft compose the majority of the aviation fleet but did not achieve 100% penetration. Fleet 311
penetration is dependent upon rates of fleet growth with time, which depend in turn on GDP and 312
population projections, and the relative oil price modeled in each scenario. The high uptake of 313
composite material aircraft in all scenarios indicates that they are cost-effective to operate in all 314
cases modeled. 315
Figure 6 (d, e and f [bottom row]) shows the modeled CO2 emissions of the global aviation 316
fleet through to 2050 for each of three socio-economic scenarios utilised in this study. Historic 317
global aviations emissions (pre-2005) collected by the International Energy Agency (IEA, 2007a; 318
17
IEA, 2007b) are plotted in addition to the simulation. CO2 emissions are predicted to be reduced 319
by between 14-15% by 2050 due to the introduction of composite aircraft, relative to the baseline 320
scenario. It should be noted that the observed discrepancy between the AIM and IEA values is 321
due to the fact that the IEA figures include all aviation, whereas AIM models 95% of scheduled 322
passenger revenue passenger kilometres RPKs. AIM does not account for freight and 323
unscheduled flights (Reynolds, 2007). Table 4 presents the numerical values for each scenario 324
output in this analysis, showing absolute values for the aviation fleets with and without the 325
implementation of composites. 326
6. DISCUSSION 327
6.1 LCA 328
The results of the LCA clearly highlight that the environmental impact of an aircraft is 329
dominated by the in-use phase. The reader should note the difference in scale between the single 330
score environmental impact of Fig. 1 (manufacturing and disposal phases) and Fig. 4 (inclusive 331
of in-use phase) being measured in kPt and MPt respectively. Despite an increased 332
environmental burden through the utilisation of CFRP at the manufacturing and disposal stage, 333
particularly as a result of fossil fuel use, this is negligible when taken into consideration with the 334
in-use phase. 335
The LCA scenarios presented for conventional aluminum airframe architecture (AL1 and AL2), 336
present onerous comparison for the CFRP. The assumption of a 100% recycled waste disposal 337
route reduced the single score environmental impact of both scenarios, due to this being deemed 338
a positive impact in SimaPro LCA software. The disposal route for CFRP is assumed to be 339
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landfill, due to the lack of current recycling routes for a relatively new and novel material 340
(Pickering, 2006; Witik, 2013) 341
6.2 Global Aviation 342
The benefits of a transition of the global passenger aviation fleet to composite material aircraft 343
goes beyond the direct 14-15% CO2 savings predicted in this study. The benefit of composite 344
material aircraft implementation also includes globally reduced fuel consumption and therefore 345
potentially lower direct operating costs, due to an improved lift-to-drag ratio and reduced weight. 346
The reduction in fuel consumption leads to reduced CO2 emissions and in addition reduced 347
emissions in all combustion products (including NOx and water vapour). The reduction in 348
engine combustion products is more beneficial than a targeted intervention solely aimed at a net 349
reduction in CO2 emissions, for example the introduction of biomass derived jet fuel. 350
The industry target of CO2 reduction by 50% on a RPK basis by 2020 cannot be achieved solely 351
by the introduction of airframes utilising a high proportion of composite material, as 352
demonstrated in this study. Though this novel lightweight technology is an important component 353
in reducing the environmental impact of aviation, it is a step change in technology that must be 354
considered in conjunction with a range of other technological and operational improvements. 355
The Advisory Council for Aviation Research and Innovation in Europe (ACARE,2002) goal of 356
reducing fuel consumption per RPK by 50% for new aircraft entering service after 2020 is split 357
between technological improvements in engine and airframe technology, 15-20% and 20-25% 358
respectively. The remainder of 50% reduction is to be achieved through improvements in 359
operational procedures air transport movements (ATM). Long-term ACARE goals through to 360
2050 include 75% reduction in CO2 emissions per passenger kilometer relative to 2000 361
19
(ACARE, 2002). The composite aircraft utilised in this study achieves the primary goal for a 362
reduction in fuel consumption for aircraft entering the fleet post-2020. To achieve the long-363
range goals of a 75% reduction would require a step change in aircraft design towards a blended 364
wing body aircraft, which presents significant technical challenges, and technology readiness is 365
predicted around 2037-38 (Vera Morales, 2011). 366
Greenhouse gas emissions from international aviation have not been included in the previous 367
international programmes to tackle global warming and anthropogenic climate change. The 368
inclusion of international aviation in the European Union Emissions Trading Scheme (EU ETS) 369
in 2012 has since been suspended pending the formation of an international agreement at the 370
2014 ICAO annual general meeting. Calls from within the aviation industry are for single 371
market based mechanism (MBM) that “... should contribute towards achieving global 372
aspirational goals” (ICAO, 2011). Presently no MBM has been developed. 373
The lifetime of an aircraft airframe can be up to 30-years (Kahn Ribeiro, 2007) and those aircraft 374
models entering service before 2020 could very well still be in operation by 2050, the end of the 375
modeling period used in this study. The predicted growth in aviation demand to 2030 alone will 376
require the delivery of between 27, 000 and 33, 500 new passenger aircraft (Airbus, 2011; 377
Boeing 2013) equating to an order value of approximately $4 trillion. As was highlighted in this 378
study the emission reduction potential of composite aircraft was limited due to fleet penetration 379
not being 100% by 2050. 380
Despite an increased environmental impact of CFRP during manufacture and disposal, the 381
section under analysis demonstrates a significant reduction in impact over its lifetime. The 382
20
reduced impact is due to the in-use phase and consumption of jet-fuel that far outweighs the 383
impact of manufacture and disposal. 384
Under all three socio-economic scenarios utilised in this study, the potential reduction in 385
emissions of carbon dioxide due to a transition of the aircraft fleet to composite materials was 386
14-15% compared to a baseline projection using current technology in 2050 – a reduction in 387
cumulative 2010-2050 emissions of 9-11%. Reductions in the emission of carbon dioxide is less 388
than the quoted technical potential of 20-25% due to fleet penetration not being total and a 389
passenger and service demand increase of 6-9% by 2050; the result of reduced operating costs of 390
composite material aircraft resulting in lower ticket prices. 391
7. CONCLUSIONS 392
The life cycle assessment demonstrates a reduction in the environmental impacts through the 393
transition of airframe architecture from conventional aluminum to CFRP. It was shown that 394
CFRP was preferable even in the most favorable aluminum scenario (low buy-to-fly ratio and 395
waste 100% recycled). Furthermore, the study highlighted how the life cycle environmental 396
impact of aircraft is dominated by the in-use phase, particularly the consumption of fossil fuels 397
and the release of CO2 and NOx related to the combustion of aviation fuel. 398
The conventional LCA presented in this study supported industry claims of a reduction in carbon 399
emissions through the introduction of composite material airframe architecture. However, the 400
secondary analysis, utilising the AIM model, demonstrates the potential reduction in carbon 401
emissions were less than predicted due to an interaction of technology and market, in this case a 402
positive rebound in demand due to lower ticket prices. 403
21
The conclusions of this study highlight the importance of creating a market based mechanism for 404
carbon dioxide that supports the market adoption of more fuel efficient aircraft but also addresses 405
potential uplift in demand as a result of the reduced operational costs of composite material 406
aircraft. The results of this study were based on a simplified CFRP tube section, due to the lack 407
of technical process data in the public arena. It is recommended that additional study should be 408
undertaken with more detailed manufacturing process data and structural airframe components, 409
both of CFRP and aluminum. An extension to this study would be to conduct a hybrid LCA to 410
estimate indirect and direct emissions from the wider supply chain. 411
8. ACKNOWLEDGMENT 412
This study has been carried out independently using the information available in the public 413
domain. The authors wish to thank Bart Moenster, John Baumann and David Heck from Boeing 414
for their motivational support. 415
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522
523
8. TABLES 524
Table 1. Break-even distances and time (hours of flying) for CFRP vs. Al1 and Al2. 525
CFRP vs. AL1
CFRP vs. AL2
Distance (km)
Time (h)
Distance (km)
Time (h)
Carbon dioxide
170 000
188
95 000
105
Nitrogen oxides
90 000
99
70 000
77
526
Table 2. Socio-economic model inputs into the Aviation Integrated Model (AIM). 527
Input
Scenario
USA
Western
Eastern
Europe/Former
China
India
Japan
Africa/Latin
America/Rest
26
Parameter
Europea
Soviet Union
of the world
Population
growth rate
%/yearb
IGSM
0.6
-0.2
-0.3
0.3
0.9
-0.2
1.3
MERGE
0.4
0.0
-0.1
0.3
0.7
0.0
1.1
MiniCAM
0.6
0.0
-0.1
0.2
0.8
-0.2
1.2
GDP/capita
growth rate,
%/yearb
IGSM
2.2
2.9
4.0
4.0
2.5
3.1
1.9
MERGE
1.4
1.7
3.4
4.5
4.3
1.3
2.5
MiniCAM
1.3
1.0
3.3
5.1
4.8
1.2
1.9
Oil price,
$2005 per
bbl
IGSM
106 (2020), 154 (2040)
MERGE
82 (2020), 124 (2040)
MiniCAM
74 (2020), 92 (2040)
a The country composition of geographic regions in each socio-economic are different and as 528
such a direct comparison of values is limited. Full country lists are presented in (Clarke et al, 529
2007) 530
b Mean values for 2005-2050 (Clarke, 2007) 531
532
Table 3. Substitute aircraft utilised and their operational performance. 533
Size Class
Large
Medium
Small
Definition (No. Seats)
>299
190-299
100-190
Reference Aircraft
Boeing 777-300
Airbus A330-300
Airbus A319-131
Reference Engine
Rolls Royce Trent 895
General Electric CF6
80E1 A2
V2511
Composite Aircraft
A350-1000
Boeing 787
TOSCA composite
aircraft
Year of Fleet Entry
2017
2012a
2025b
Purchase Price ($m)
205.8b
148.7c
67.0b
Maintenance Cost
30% lower than reference aircraftd
Fuel Use (against
reference aircraft)
25% lowere
20% lowerf
22% lowerb
Notes 534
27
a Closest full year of operation. First fleet entry late-2011. 535
b TOSCA mid-range estimate (Vera Morales, 2011) 536
c Average of Boeing 787 subtypes. Assumed 20% discount from list price 537
d TOSCA estimate. Boeing 787 factsheet relative to ‘comparable aircraft types’ (Boeing, 538
2013b)
539
e Airbus 350 factsheet relative to ‘current competitor’ (Airbus, 2012)
540
f Boeing 787 factsheet relative to ‘comparable aircraft types’ (Boeing, 2013b) 541
542
Table 4. A summary of the outputs for each scenario in AIM analysis. 543
Output
Parameter
Scenario
2005
value
2020 value
2050 value
No
Composites
Composites
No
Composites
Composites
Direct
CO2, Mt
IGSM
510a
1025
993
3917
3333
MERGE
1019
996
3485
2994
MiniCAM
976
957
3247
2796
Direct
CO2, Mt
per pkmb
IGSM
0.135
0.125
0.118
0.127c
0.100
MERGE
0.125
0.120
0.127
0.103
MiniCAM
0.125
0.121
0.127
0.105
Global
fleet,
number
IGSM
18100
29900
30400
92000
97900
MERGE
29400
29600
80300
84500
MiniCAM
28200
28400
74600
77800
a IEA (2007) give global direct aviation CO2 in 2005 as 725 Mt; this includes freight and 544
unscheduled flights which are not modelled in AIM. 545
b Since freight is not directly modelled in AIM, we use passenger kilometers (pkm) as a basis for 546
comparison rather than tonne-kilometres (tkm) here. 547
c The rise in CO2 per pkm reflects changing use patterns of aircraft; for a given individual flight 548
emissions in this scenario are similar to those in 2020. 549
28
550
9. FIGURE CAPTIONS 551
Figure 1 Single score environmental impact comparison of the three scenarios: Al1 (BTF ratio 552
1:1), Al2 (BTF ratio 8:1) and CFRP section in manufacturing and disposal phase. 553
Figure 2 Normalization plot of environmental impact for the three scenarios by impact category. 554
Figure 3 Quantities of CO2 and NOx produced in manufacturing and disposal of composite 555
airframe section. 556
Figure 4. A complete LCA single score environmental impact comparison of the three scenarios 557
used in this study. 558
Figure 5. Quantities of CO2 and NOx produced from the complete LCA of the three scenarios 559
used in this study. 560
Figure 6 Modeled fleet penetrations of composite aircraft (top). Modeled emission of CO2 561
through to 2050 (bottom). 562
10. FIGURES 563
29
564
565
30
566
567
31
568
569
